PASSAU, West Germany (AP) _ Three weeks ago, Lothar Klein asked his frail and aging mother if he should head to Hungary in search of eventual freedom in the West.

''She had tears in her eyes and gave me a hug,'' said the burly 27-year-old electrician from Weimar. ''She told me, 'Son, you've got to try it now while you have a good chance.'''

Klein is among thousands of East Germans who seized the opportunity to flee their Communist homeland after Hungary agreed to allow them passage to the West.

Frequently, the decision was difficult and painful.

''Even though I knew I had to go, it was hard to leave,'' Klein said, his voice choked with emotion. ''I might never see her again.''

The East German exodus comes amid widespread pressures for democratic reforms across the East bloc. Poland has become the first Warsaw Pact nation to install a government led by non-communists. Hungary also is on the road to major reforms. But East Germany remains one of the East bloc's most rigidly controlled states and has rejected calls for change.

Refugees said they left because they no longer could bear the conditions.

For many, the reality of their successful flight is just taking hold in a jumbled emotional mixture of joy, wonder and longing for those left behind.

''It's hard to leave everything behind - your family, friends and possessions. But then you look at your children and you say to yourself 'No, I'm not going to let this happen to them. I'm not going to let the perverse system ruin them,''' said Manfred Lutz, a 35-year-old electrical engineer from Jena.

Lutz said he was ostracized increasingly at his research institute after criticizing several of its management policies. ''The system is so rigid. If you speak out, you're branded as a troublemaker and shuttled off to a less desirable job.''

Outside a crowded refugee center in downtown Passau, young East German couples wait impatiently in line to call home from a bank of public telephones.

Inside the booth, the wait will be longer still as constant busy signals remind them of the frustrating lack of phone lines in their homeland.

''We've been trying for hours to call home,'' sobbed a woman in her early 20s. ''Our parents still don't know we left.''

Most refugees left with only a few hastily packed belongings.

''We didn't really want for any material comforts,'' said Sabine Schoenborn, an outgoing mother of two who instructed athletes in Leipzig. ''But life there becomes intolerable when you finally realize with horror that the system is not going to change, not in your lifetime and probably not in your children's.''

Her husband, Juergen, said the family lived comfortably because of their careers in sports, a major source of international prestige for the nation of 16.6 million.

''I helped train some of our best athletes. But you can't live without hope, and that fades quickly when you recognize how impenetrable the system really is,'' said Schoenborn, wearing a faded jeans jacket over a new jogging suit bought in Passau's teeming shopping mall.

Even before they left Leipzig, the Shoenborns said they could see the growing impact of the exodus.

Neighborhood shops had been forced to close because all the workers had left, he said, and their nearby medical clinic was left with only a few overworked doctors.

Frank Kuhnert, a 29-year-old stage-lighting technician who worked at East Berlin's Deutsches Theater, said the frustration of not being able to travel abroad and ''unnecessary day-to-day hassles'' prompted him to give up a prestigious job.

''I simply got tired of having to crawl to petty officials for every little thing. You're treated like a child by goons with privileges whose job it is to see that you don't get any,'' he said.

His request to join the stage crew that went abroad on company tours repeatedly was denied, he said.

''So you end up listening to other people's stories about how great it was outside beyond the (Berlin) Wall.''

Many refugees expressed concern that their departure could make things worse for those who stay behind.

''Some people told us we would just make it harder for those who can't or don't want to leave,'' said Katrin Albrecht, a 24-year-old music student from Dresden.

''But you have to do what you think is right, even if it's painful. I just hope that what I and others have done will force the government to wake up and listen to the people clamoring for change, for a little dignity in their lives,'' she said.